This disclosure relates to fracture-resistant layered-substrates, articles and devices including such layered-substrates and methods for making such layered-substrates, articles and/or devices. More particularly, this disclosure relates to layered-substrates including a substrate and a layer that are able to withstand fracture when assembled with an article (e.g., electronic device, architectural structures, appliances, automotive components, etc.) that is dropped onto a drop surface or that exposed to other objects being dropped thereon.
Articles such as electronic devices (e.g., mobile phones, smart phones, tablets, video players, information terminal devices, laptop computer, etc.), architectural structures (e.g., countertops or walls), appliances (e.g., cooktops, refrigerator and dishwasher doors, etc.), information displays (e.g., whiteboards), and automotive components (e.g., dashboard panels, windshields, window components, etc.) incorporate various substrates as internal components or external components. When used in such articles, the substrate can be part of a housing or a display. When used in a display, the substrate may be referred to as a cover substrate and, in some instances, may form part of a touch module. Cover substrates are often transparent and scratch-resistant. Substrates used as housing can form the sides, back and front portions of housing and may exhibit scratch-resistance and opacity, instead of exhibiting transparency.
With continuing efforts to make some articles or components of articles lighter and thinner and to include even greater functionality, substrates, whether used as cover substrates or housing substrates, are becoming thinner. As substrates become thinner, they are also more susceptible the damage that can occur during normal use of articles incorporating such substrates. It has become more important to develop substrates having improved survivability, especially when subjected to tensile stresses caused by contact with hard/sharp surfaces, such as asphalt or concrete and/or falling objects, experienced in “real world” use and applications.
Moreover, there is a need for such substrates to exhibit resistance to scratches that cause abrasion damage and/or scratches that cause single event scratch damage. Single event scratch damage can be contrasted with abrasion damage. In some cases, substrates used as external components in devices, such as electronic devices, do not typically experience abrasion damage because abrasion damage is generally caused by reciprocating sliding contact from hard counter face objects (e.g., sand, gravel and sandpaper). Instead, cover substrates typically endure only reciprocating sliding contact from soft objects, such as fingers. In addition, where such substrates are combined with layers (or coatings), abrasion damage can generate heat, which can degrade chemical bonds in such layers and can cause flaking and other types of damage. As abrasion damage is often experienced over a longer term, the layer disposed on the substrate that experiences the abrasion damage can also oxidize, which further degrades the durability of the layer and thus the layered-substrate. The single events that cause scratch damage generally do not involve the same conditions as the events that cause abrasion damage and therefore, the solutions often utilized to prevent abrasion damage may not prevent single event scratch damage in substrates or layered-substrates. Moreover, known scratch and abrasion damage solutions often compromise the optical properties, which is not acceptable in most uses of substrates, layered-substrates or articles incorporating the same.